Christchurch police say there could be more to a serious road rage incident after the alleged attacker came forward to tell his side of the story.
A 37-year-old man suffered serious facial injuries when he was allegedly attacked on Johns Rd in Harewood on January 6.
The man's 80-year-old father, who was the front-seat passenger, watched on as the incident unfolded.
The victim then managed to drive himself to hospital, where he underwent surgery before being discharged last week.
Detective Sergeant Mark Worner said a witness and the alleged offender had since come forward and were interviewed last night.
Mr Worner said police would talk to the victim again tomorrow before making a decision on whether any charges would be laid.
"We haven't had a chance to talk to him since he initially made his statement. He hasn't been well enough to speak to.''
Mr Worner said he was pleased the other person had come forward.
"They said that they had made the decision to come forward because they wanted to tell their side of the story,'' he said.
"If what they say is closer to the point, there's a little bit more to it than initially reported.''
Mr Worner would not go into detail about the alleged offender's version of events.
The victim told police last week that the incident took place after he overtook a blue Isuzu Bighorn truck, which had been driving very slowly down Johns Rd.
The truck's driver then took exception to being overtaken.
"He came up behind him and was tooting and flashing his lights, overtook him again, slammed on his brakes and forced him to pull over to the side of the road.''
The driver of the Bighorn allegedly assaulted the man on the roadside.
The victim is not expected to be able to return to work until next month.